Filter medium.



No. 875,355. PATENTED DEC. 31, 1 907.

ELM. KNIGHT. FILTER MEDIUM.

APPLIOATION FILED JULY 24,1907,

WITNESSES INVENTOR di k M47412? ATTOQNEV A broken away. Fig 2 is a section t j UNI E STATES PATEnToFFroE.

EDWARD M. KNIGH or SAN rnANcIsco, GA

LIFORNIAJ F TER minimum,

Specification of Letters Patentfi I Patented Dec. 31,1907.

ama filed m 24.1907.- Serial No. 385,267.

To all whom it may concern:

Be it known that I, EDWARD M. K IGHT,

a citizen of the United States, residing in the city and county of San Francisco and State of California, have invented new and useful Improvements inFilter Mediums, of which the following is a s ecification.

This invention re ates to filtering pads for.

that class of filter which acts under direct pressure from the main, and the said inven tion has for its object the provision of a fibrous filtering medium of asbestos and carbon, having a novelstructure, and made sufficiently strong to withstand heavy pressure.

Referring to the accompanying drawings, for a more complete explanation ofmy inventionFigure 1 is a plan view with plortion XX of Fig. 1.

Ithas been found in practice that two layers of compressed asbestos fiber will-not adhere permanently, whether carbonated or uncarbonated. Hence the difiiculty, hitherto, of manufacturing filtering'media ofthis material.- The method I ropose to adopt in the constructionfof niy. tering pad is one in which the joints are formed from the uncompressed asbestos, the fibers of which readily interlock, the layers of carbon and asbestos becoming thereby interstratified.

For the purpose of myinvention I take a shallowtray, square, round or oval, according to shape of pad required. In the tray I area.

place carded asbestos A, spreadingitevenly,

and then compress a part thereof, e. g. the

central ortion, about one-third of the whole his compressedportion I carbonate, by spreading over it an even layer of carbon 2, preferably in the form of paste. This car bonated area, and the uncarbonated and uncompressed area are next covered with carded asbestos. I then compress a zone, 3

concentric with the carbonated portion, and in area about one-third of the whole area 8f the pad. This zone is then carbonated at 4 in the same manner as above described with referencetothe central portion, and a layer of carded asbestos is so placed that it covers the newly carbonated area thickly, and the uncarbonated area lightly. The re mainingportion of the surface, as yet untreated, is, in its turn, compressed, carbonrough portions. The whole pad is then compressed. The result of this process is a pad,'carbonatedthroughout and firmly held. together by the interstratification of the carbon and asbestos, and by the interlacing of the asbestos fibers.

I do not confine myself to three stages in the manufacture of my improved filtering pads, asit is obvious I may have more than three stages, orin some; cases only two.

In pads made as heretofore the asbestos layers-confining. the carbon are fastened together only at the edges; Therefore, in pads oflar e area, the weight of the carbon, being 'entirey unsup orted at thecenter,-causes theasbestos to reak away at the joints, and the pad becomes practically useless. By my improved method the asbestos and carbon layers are'fastened together throughout their-surfaces, and are therefore very strong bon are inter'stratified with the asbestos.

2. The process of preparing filter mediums, said process consisting in superposing alternate zones of asbestos and carbon concentrically, so that the carbon isinterstratiated and covered with carded asbestos in exactly the same manner-as the two previous fiedand held in place by the interlocking of the asbestos fiber.

3. The ro'cess of-making filtering pads or disks, sai process consisting in forming a disk with loose uncompressed asbestos fiber, then compressing aqj ortion of it and coating it with carbon, superposin another disk of asbestos fiber so that its 'bers will cover the carbonatedportion of the first disk, and 100 also interlock wlth the fibers of the first disk,

then compressing andcoatiiig a portion of said second disk of asbestos fiber, and in the same or like manner adding successive disks g srmese of asbestos fiber and carbon to form a pad of I and intermediate ortions coated with. csrasbestos interstratified with carbon over the bon, interstretifiewith the asbestos. Whole area- 4 In testimony whereof I have hereunto set 4. As an article of manufacture, a filtering my hand in presence of two subscribing wit 5 ad consisting of sufierposed and interlocke v nesses. I

ayers 0 asbestos, eving-inte osed zones v T v of carbon interstratified with t e asbestos. EDWARD KNIGHT 5. As an article of manufacture, a filtering Witnesses: I pad consisting of superposed layers of asbesl GEO. H. STRONG,

10 tos having portions of their area interlocked l S, H. N OURSE. 

